The present embodiments relate to a local antenna device for transmitting magnetic resonance (MR) signals of a number of MR receiving antenna elements to an MR signal processing device.
Imaging systems in medical technology play a significant role in the examination of patients. The images of the patient's internal organs and structures that are generated by the imaging systems are used in the diagnosis of the causes of disease, the planning of operations or the performance of operations or for the preparation of therapeutic measures. Examples of imaging systems of this kind include ultrasound systems, X-ray computed tomography (CT) systems, positron emission tomography (PET) systems, single photon emission tomography (SPECT) systems and MR systems. In the MR systems, during the MR examination, local coils may be used for receiving the MR signals of the examination subject. The local coils are MR receiving antenna modules that contain MR receiving antenna elements (e.g., in the form of conductor loops). During the examination, the local coils are arranged relatively close to the body surface, wherever possible directly on the patient's organ or body part that is to be examined. Unlike relatively large antennas that are arranged further away from the patient, local coils have the advantage that the local coils are arranged closer to the regions of interest. The noise level caused by the electrical losses within the patient's body is reduced, and this has the result that the signal-to-noise ratio (SNR) of a local coil is better than the SNR of an antenna that is further away.
The MR signals that are received by the MR receiving antenna elements may be preamplified while the MR signals are still in the local coil and then fed, by way of cables, out of the central region of the MR system to a shielded receiver of an MR signal processing device. At the shielded receiver of the MR signal processing device, the data received is digitized and processed further for generating images. Where there is a relatively large number of MR receiving antenna elements, there is consequently also a greater need for cables for transmitting the MR signals. However, a large number of cables slows down the attachment of the local coils to the examination subject, resulting in longer treatment times and, hence, higher treatment costs. Many patients find the cables troubling. Further, the examination space is delimited inside an MR system, which limits the use of a large number of cables (e.g., if the patient is moved on an associated table arrangement). The above-mentioned restrictions may be the case if analog MR signals are transmitted by the receiving antenna elements, since shielded (coaxial) cables may be used. The shielded cables are large in cross section, heavy and expensive.
There is, therefore, a need for solutions for transmitting the MR signals to the MR signal processing device that reduce the number of cables needed or avoids the cables completely.
US 2007/0182409 A1 describes an MR system, in which the MR signals are transmitted to a processing device not by way of cables but wirelessly (e.g., by way of optical signals). However, the use of optical signals may require a direct line of sight between the transmitter and the receiver, resulting in corresponding restrictions on the handling of the local coils. WO 2009/081378 A1 provides, for an MR system, a local coil that may both receive and transmit signals wirelessly.